Impaired retinal processing in regular cannabis users: Potential benefit of electroretinogram as a biomark

Cannabis is one of the most prevalent drugs used in industrialized countries. Regular cannabis use is associated with impairments in highly integrative cognitive functions such as memory, attention and executive functions. However, the neural impact of cannabis use remains poorly understood. Elucidating the cerebral mechanisms underlying these deficits represents now a crucial step in addictive disorders. The retina is a part of the central nervous system due to its embryonic origin thereby reflecting the neurochemistry of the brain. Furthermore its measure is well standardized allowing good reproducibility. Considering the anatomical and functional distribution of endocannabinoids in the retina [1] , we evaluated the retinal function in regular cannabis users and healthy control subjects. Recordings of flash electroretinogram (fERG) were performed in regular cannabis users and healthy controls using guidelines of international society for clinical electrophysiology of vision (ISCEV) [2] . Both amplitude and implicit time of a-wave and b-wave were assessed in scotopic and photopic conditions. Measurements of fERG showed increased implicit time of a-wave and b-wave in both photopic and scotopic conditions in regular cannabis users compared to healthy controls. These findings suggest that retinal processing may be altered at the level of photoreceptor and bipolar cells in regular cannabis users. These results are consistent with previous reports in animal species, which show the involvement of the cannabinoid system in the regulation of the retinal metabolism thus leading to alterations of fERG measurements. Since alterations in the central neurotransmission may affect the ERG measurements, the retina might constitute a possible biomarker of brain disorders in addictive diseases [3] .